1. Field of the Invention
This invention relates to an anti-pilfer lock device for protecting against unauthorized access to the flow control valve units projecting from the outer surface of a mobile ammonia nurse tank. In particular, the invention concerns an anti-pilfer housing configured to the to be removably placed over the flow control valve units of an ammonia nurse tank and that can be locked in place to prevent unauthorized removal of ammonia from the tank.
In particular, the box-shaped housing of the anti-pilfer lock device has a lower edge which is configured to complementally engage the outer cylindrical surface of an ammonia nurse tank, along with lock structure engageable with the flow control valve units of the tank and that is cooperable with a lock assembly for releasably locking the housing in the anti-pilfer disposition thereof on the tank. Upon unlocking of the lock structure, the protective housing may be removed from the nurse tank while the lock structure engageable with the flow control valve units remains in place. In this manner, the lock assembly may simply be unlocked and the protective housing removed from the tank for the user to gain access to the flow control valves. When it is desired to return the housing to the tank in blocking relationship to the flow control valves, that may be accomplished by simply returning the housing to its protective position on the tank followed by locking of the lock assembly.
2. Description of the Prior Art
Anhydrous ammonia has long been used as a fertilizer for crops. The ammonia is introduced into the soil by each of a series of nozzle assemblies operably associated with a tool pulled by the tractor that penetrates the soil. In order to minimize the ammonia application time in the field, many farmers purchase anhydrous ammonia from a central supplier who stores the liquid product in a relatively large, horizontally exposed bullet tank typically capable of storing anywhere from 20,000 to 100,000 gallons of liquid product. The supplier of the liquified ammonia often maintains a fleet of mobile cylindrical storage vessels known as nurse tanks that are on wheels and that may be towed as a trailer behind a vehicle. These mobile nurse tanks, each of which may be from three to four feet in diameter and 10 to 14 feet in length, are individually filled with liquified anhydrous ammonia upon order by a farmer, and then towed over the road to a point of application.
Typical mobile nurse tanks have external inlet and outlet flow control inlet valves, a flow control valve for return of vapor or liquid to the tank, and at least one gauge and at least two gauges which show the pressure that exists within the vessel, as well as the quantity of liquid remaining in the tank. These valves and gauges project outwardly from the outer cylindrical surface of the nurse tank. Some of the nurse tanks have roll bar structure associated with and located on opposite sides of the flow control valves and gauges to prevent damage to the valves and gauges in the event of inadvertent overturning of the tank.
Not infrequently, a farmer does not apply the entire quantity of anhydrous ammonia contained in a nurse tank during each day of fertilizer application. In certain instances, the farmer may not apply liquid anhydrous ammonia stored in the nurse tank until several days have elapsed from the time the mobile tank is first driven to a field storage location. As a consequence, ammonia may be surreptitiously removed from a nurse tank containing anhydrous ammonia while the tank sits unprotected in a usually remote field location. Such theft of ammonia is most often carried out under the cover of darkness. A hose may be attached to the outlet flow control valve of the tank and the control knob simply rotated to permit the pressurized ammonia tank to flow outwardly into a relatively small storage container.
The problem of theft of anhydrous ammonia stored as a liquid in mobile nurse tanks left at a relatively remote location in a farmer""s field has been exacerbated in recent years because of the growing use of ammonia as a component in the illicit manufacture of methamphetamine. Processes for making methamphetamine are widely publicized, including internet sites, and sophisticated equipment is not required to produce the drug in limited space. As a consequence, farmers are more and more finding that ammonia is being stolen from nurse tanks that are left out in the field overnight or for days.
It is not practical to maintain constant surveillance over a nurse tank left out in a field, and inconvenient to pull a nurse tank into a location near the farmer""s house each evening during use, or after partially being emptied and then not used again for several days. Even if the farmer did return the tank to a storage area near his house, persons bent on stealing ammonia from the tank could in some circumstances do so after dark.
The anti-pilfer lock device of this invention is a simple, effective and efficient way of preventing unauthorized removal of anhydrous ammonia from a mobile nurse tank. The device includes a housing configured to be removably mounted on the nurse tank in a position shielding the flow control valve units which project from the external surface of the tank from unauthorized access. Lock structure is provided which includes a lock assembly that is accessible externally of the housing, and components releasably joined to the lock assembly and engageable with at least one of the control valve units. The lock structure is cooperable with the housing for maintaining the housing in its flow control valve shielding position until the lock assembly is unlocked and housing is removed from the nurse tank.
The lock structure components include a coupling element that is positioned adjacent the flow control valve units when the housing is mounted on the nurse tank in the control valve unit shielding position, a connector assembly for connecting the coupling element to at least one flow control valve unit, and an extension releasably joining the coupling element and lock assembly when the housing is mounted on the nurse tank in said control valve unit shielding position. The coupling element preferably comprises an elongated bar adapted to be positioned alongside the valve control units, and a U-bolt assembly connecting the bar to a respective flow control valve body. The extension preferably comprises an upright strap member connected to the bar and extending through an opening therefor in the upper wall of the housing when the housing is supported on the shell of the nurse tank in enveloping relationship to the control valve units.
The upper end of the extension bar or strap which projects beyond the upper surface of the housing has an opening therein which removably receives the bolt of a lock that rests on the upper surface of the protective housing.
The coupling bar and U-bolts joining the coupling bar to the body portion of each of the flow control valve units, as well as the extension strap member connected to the coupling bar remain in place when the lock is unlocked and the protective housing removed from the nurse tank. Full access may thus be had to the control valve units for filling of the tank or removal of anhydrous ammonia therefrom. Reversal of such sequence results in return of the housing to its position in protecting relationship of the flow control valve and gauges projecting outwardly from the shell of the nurse tank.
Advantages of the anti-pilfer device of this invention include a simplicity of the design and parts, and the ease of installation and use. The anti-pilfer device may be used on tanks of various diameters with the only requirement to be to configure the lower edge of the housing to complementally engage a particular tank circumference. The anti-pilfer device does not impede on the integrity of the tank or in any way limit transport thereof behind a pulling vehicle. If desired, the housing may be constructed of a size to cover just the flow valve control units and the gauges projecting from the surface of the tank, or fabricated of a larger size to also enclose and envelope any roll bars on the outer surface of the tank and which are associated with the valve control units.
In addition, no modification of a nurse tank itself is required, and therefore no tank manufacturer/engineering review is required to install the anti-pilfer device on an existing nurse tank. Finally, the anti-pilfer device is relatively inexpensive to fabricate and requires little if any maintenance.
The improved design characteristics of the anti-pilfer device for ammonia nurse tanks, and favorable cost factors makes use thereof attractive to nurse tank fleet operators as a standard item on all of their nurse tanks.